>Nikon seems to factor in writing to a "normal" card >in calculating the buffer.
You may be right. I notice on my D7000 that going to 12-bit lossy mode doesn't show the same number of buffer frames in the camera as are shown in the manual. But if the numbers aren't exact, the effect is still present. Writing faster to the card clears the buffer more quickly. This is obvious if you compare fast and slow cards in a camera. For example, with a Sandisk 95 MB/s UHS-I card in my D7000 in 12-bit lossy mode where the camera shows a buffer of 11, I can go about 18 shots before things slow down. With a crappy old SD card (not sure of the speed), I get about 13 shots.
>I would add that most RAW shooters will shoot either 12 or 14 >bit lossless.
How do you know that? Anecdotally, I know plenty of raw shooters who use the lossy modes. And I think if the tradeoff of going to lossy compression is a substantially higher frame rate, many would choose to make that tradeoff. Even at 12-bit lossy you are gaining most of the advantages of using raw.